Neurosteroids represent a novel class of endogenous compounds that have the ability to exert rapid, nongenomic effects and produce various endocrine and behavioral effects. The role of these steroids in the behavioral effects of ethanol has received much recent attention. In the behavioral assay of drug discrimination, neurosteroids such as allopregnanolone and pregnanolone produce discriminative stimuli that are very similar to ethanol. These behavioral effects of neurosteroids need to be thoroughly examined to understand the role of these endogenous compounds in ethanol's actions. Drug discrimination is commonly used to identify candidate receptor mechanisms underlying the behavioral effects of drugs. This research proposal aims to extensively characterize the behavioral effects of pregnanolone through drug discrimination in DBA/2J and C57BL/6J inbred mice. Also, this research for the first time will compare the discriminative stimulus effects of pregnanolone with the motor effects of pregnanolone on schedule-controlled behavior to obtain an adequate picture of the subjective and motor behavioral effects of the neurosteroid pregnanolone.